Hi Gu,
Investigation shows, that f2fs_evict_inode, when called for 'meta_inode', uses
invalidate_mapping_pages() for 'node_inode'.
But 'node_inode' is deleted before 'meta_inode' in f2fs_put_super via iput().
It seems that in common usage scenario this use-after-free is benign, because
'node_inode' remains partially valid data even after kmem_cache_free().
But things may change if, while 'meta_inode' is evicted in one f2fs filesystem,
another (mounted) f2fs filesystem requests inode from cache, and formely
'node_inode' of the first filesystem is returned.
The analysis seems reasonable. Have you tried to swap the reclaim order of
node_inde
and meta_inode?
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 870fe19..e114418 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -430,8 +430,8 @@ static void f2fs_put_super(struct super_block *sb)
if (sbi->s_dirty && get_pages(sbi, F2FS_DIRTY_NODES))
write_checkpoint(sbi, true);
- iput(sbi->node_inode);
iput(sbi->meta_inode);
+ iput(sbi->node_inode);
/* destroy f2fs internal modules */
destroy_node_manager(sbi);
Thanks,
Gu
With reclaim order of node_inode and meta_inode swapped, use-after-free
error disappears.
But shouldn't initialization order of these inodes be swapped too?
As meta_inode uses node_inode, it seems logical that it should be
initialized after it.
--
Best regards,
Andrey Tsyvarev
Linux Verification Center, ISPRAS
web:http://linuxtesting.org
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